Can't update/upgrade du to "Could not execute 'apt-key' to verify signature"

Question

I installed Ubuntu 16.04 last week on my server on a Digital Ocean droplet and since then I can't update nor upgrade anything on my server. Ma version Linux 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9 19:31:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

I get this error after a sudo apt-get update :

Get:1 http://ppa.launchpad.net/ondrej/php/ubuntu xenial InRelease [23.9 kB]
Ign:1 http://ppa.launchpad.net/ondrej/php/ubuntu xenial InRelease                                                                          
Hit:2 http://security.ubuntu.com/ubuntu xenial-security InRelease                                                                    
Get:3 http://us.archive.ubuntu.com/ubuntu xenial InRelease [247 kB]                                       
Err:2 http://security.ubuntu.com/ubuntu xenial-security InRelease
  Could not execute 'apt-key' to verify signature (is gnupg installed?)
Err:3 http://us.archive.ubuntu.com/ubuntu xenial InRelease     
  Could not execute 'apt-key' to verify signature (is gnupg installed?)
Hit:7 http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease
Err:7 http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease
  Could not execute 'apt-key' to verify signature (is gnupg installed?)
Hit:8 http://us.archive.ubuntu.com/ubuntu xenial-backports InRelease
Err:8 http://us.archive.ubuntu.com/ubuntu xenial-backports InRelease
  Could not execute 'apt-key' to verify signature (is gnupg installed?)
Fetched 272 kB in 0s (363 kB/s)
Reading package lists... Done
W: GPG error: http://ppa.launchpad.net/ondrej/php/ubuntu xenial         InRelease: Could not execute 'apt-key' to verify signature (is gnupg installed?)
W: The repository 'http://ppa.launchpad.net/ondrej/php/ubuntu xenial InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://security.ubuntu.com/ubuntu xenial-security InRelease: Could not execute 'apt-key' to verify signature (is gnupg installed?)
W: GPG error: https://apt.dockerproject.org/repo ubuntu-xenial Release: Could not execute 'apt-key' to verify signature (is gnupg installed?)
W: The repository 'https://apt.dockerproject.org/repo ubuntu-xenial Release' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://us.archive.ubuntu.com/ubuntu xenial InRelease: Could not execute 'apt-key' to verify signature (is gnupg installed?)
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease: Could not execute 'apt-key' to verify signature (is gnupg installed?)
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://us.archive.ubuntu.com/ubuntu xenial-backports InRelease: Could not execute 'apt-key' to verify signature (is gnupg installed?)
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/xenial/InRelease  Could not execute 'apt-key' to verify signature (is gnupg installed?)
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/xenial-updates/InRelease  Could not execute 'apt-key' to verify signature (is gnupg installed?)
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/xenial-backports/InRelease  Could not execute 'apt-key' to verify signature (is gnupg installed?)
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/xenial-security/InRelease  Could not execute 'apt-key' to verify signature (is gnupg installed?)
W: Some index files failed to download. They have been ignored, or old ones used instead.

I checked for apt-key which is there and working.

Solution 1

I had the same problem on my Ubuntu droplet at Digital Ocean (after a distro upgrade).

Just upgrade your kernel in the digital ocean administration site (yes, it's weird). There is a "kernel" option in the menu on the left side where you can select a new kernel image.

In my case the upgrade was from 3.x to 4.x series

Solution 2

Changing the permission of /tmp back to their defaults worked for me:

sudo chmod 1777 /tmp

Solution 3

In my case I played with AppArmor and enabled complain mode on sshd. Disabling it by aa-disable /usr/sbin/sshd and re-connecting fixed my problem.

Comments

[ddattee]

For a part solution I added Digital Ocean repository mirrors with which the system had no problem so I have been able to update my applications and my system. But the problem is still here and the update fail for all official repos

[wangguoqin1001]

I've got these errors too, and haven't found a way to solve it. Replacing repositories with Digital Ocean ones doesn't work, and my investigation shows that there might be some call errors with apt-get, apt-key and /usr/lib/apt/methods/gpgv, but no further information with strace or bash debugging. Well one more clue: this is the only server of mines on DO which is running on i386 (surprisingly).

[deivid]

Same problem here... Digital Ocean, 16.04 i386 involved too.

[ddattee]

Thanks for the reply unfortunetly I got rid of the server with the problem and bought a new one (the old one was 4 years old :p) so I cannot test this but it seem like a good solution. I'll let anyone who has this problem try the solution and tell me if it fixes the problem.

[wolfog]

thanks ,this works for me